Breakaway base support for roadside standards



July 21, 1970 I sco ET AL BREAKAWAY BASE SUP-PORT FOR ROADSIDE STANDARDSFiled April 25. 1968 AflOrneys United States Patent Office 3,521,413Patented July 21, 1970 3,521,413 BREAKAWAY BASE SUPPORT FOR ROADSIDESTANDARDS Mertz 0. Scott, 869 E. 28th St. 94610, and Clive E.

McClure, 12120 Tartan Way 94619, both of Oakland, Calif.

Filed Apr. 25, 1968, Ser. No. 724,098 Int. Cl. E04b 1/41 US. C]. 5298 3Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field ofthe invention This invention relates to poles for placement adjacenttraffic carrying surfaces on highways, streets, parking lots, etc.,which are severed from their supporting surface when struck by avehicle.

State of the prior art Rigidly mounted poles such as lamp posts ortraflic standards, for example, adjacent traffic carrying surfaces ofstreets and highways present serious hazards to vehicles over whichcontrol has been lost. Particularly adjacent high-speed freeways andoverland routes, collisions between such vehicles and rigidly mountedpoles can result in serious injuries or fatalities as well as inextensive property damage. In recognition thereof, poles have beenconstructed which break away from their foundation when struck by amoving vehicle.

Several such constructions are found in the prior art. In one of them,at least a lower portion of the post adjacent the foundation isconstructed of a brittle concrete having a low impact resistance. Otherdesigns utilize slip joints between the post and the foundation in whicha horizontally acting force, such as a force from a striking vehicle,moves the post relative to its foundation until it becomes disengagedtherefrom. It is also known to provide mounting screws or studs anchoredin the foundation with an undercut to weaken them and permit theirseverance when the post is struck by a vehicle. In the latter instancethe studs are, of course, constructed so that they can withstand forcesfrom the weight of the post, the lamp or sign mounted thereon as well aswind loads acting on the post. Once the studs have been broken, new onesmust be placed in the foundation before another pole can be erected atthe site. If the foundation is of concrete and the studs are anchored inthe concrete, which is the by far most convenient method for mountingposts adjacent streets and highways, the foundation must be replaced.This is not only expensive but also time consuming. During the timeinterval it takes to replace the foundation a needed light, traflicsign, etc. is absent, thereby creating a new traflic hazard.

Although the prior art break-away poles may be satisfactory onceinstalled, they are relatively expensive to install and they are notadapted to convert rigidly mounted poles into safety break-away posts.Traditionally, rigidly mounted poles are formed with a base flange whichis mounted on a concrete foundation platform and bolted thereto by aplurality of studs cast in the concrete base. The flange is formed withopenings spaced and dimensioned to receive the studs therethrough, andthe assembly is secured by nuts threaded on the upper ends of the studsand clamping the flange to the concrete foundation. The large number oflighting poles, traflic signs, etc. presently existing and rigidlymounted makes it economically unfeasible to convert even a smallpercentage thereof into break-away posts constructed according to theprior art. Thus, the rigidly mounted poles together with the safetyhazard they present, remain in place until they must be replaced due totheir obsolecense, ill state of repair, damage from having been struckby a vehicle or roadway relocation.

SUMMARY OF THE INVENTION The present invention provides means which aresimple and inexpensive to manufacture for constructing breakaway polesor standards for use adjacent vehicular traflic carrying surfaces suchas freeways or highways, for example. It is also adapted for use withconventionally constructed rigid posts and foundations. Thus, it isadapted for erecting new poles as well as for converting existing,rigidly mounted poles into break-away poles.

Briefly, the present invention comprises elongated break-away membersadapted to be secured to the upwardly projecting ends of studs anchoredin the ground. The members have cross sectional areas which are capableof withstanding forces imparted upon them by the weight of the posts,signs or lamps mounted thereon as well as wind and ice loads acting onthe post. The members are further constructed of a material having arelatively high tensile and compressive strength but a low impactstrength so that a horizontally acting impact load will sever them andthe pole breaks away from the foundation.

In the presently preferred form of this invention, the members areconstructed of a heat treated steel. They are also made corrosionresistant, to prevent a gradual weakening of the reduced cross sectionalareas and possible failure of the members under static loads. They are,therefore, preferably constructed of a corrosionresistant material ortheir outer surfaces are suitably coated such as by plating or hot dipgalvanizing.

Aside from the primary purpose of this invention of providing low-cost,yet most effective break-away highway posts and standards, itadditionally provides an easy, low-cost installation of the pole.

Since break-away poles constructed in accordance with this inventionemploy poles and foundations constructed identically to presentlyinstalled rigid posts and standards, it is easy, inexpensive and,therefore, economically feasible to convert rigid poles into break-awaypoles. Accordingly, the present invention also provides a method forsuch a conversion. Briefly, the method includes the steps of disengagingthe upright poles from its foundation and mounting the elongated memberon the anchoring studs projecting from the foundation. Thereafter, theupright pole is lowered onto the elongated member and secured thereto.While the pole must be raised to enable the installation of thebreak-away members, it is normally not necessary to disconnect electriclines which may be connected to the top of the pole. Time consuming andhigh priced skilled labor is thereby saved. Thus, presently installedrigid lamp poles and traffic standards may be converted into break-awaypoles and standards rapidly and at relatively low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional view ofthe break-away base support for lighting poles and the like constructedin accordance with the present invention.

3. FIG. 2 is antenlarged plan view, in section, taken on line 2-2 ofFIG. 1; and

FIG. 3 is a fragmentary enlarged sectional view taken on line 3-3 ofFIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a lamp poleis anchored in its foundation block 12 and comprises an upright pole orstandard 14, an arm 16 extending transversely to the post and a lamp 18secured to the outermost end of the arm. A plurality of anchor studs 20project from the upper end of the foundation block and have theirprojecting ends externally threaded (see FIG. 3). The lower end of post14 has a mounting flange 22 which includes mounting holes 24 (shown inFIG. 3) through which elongated break-away members 26 extend. Aninternally threaded sleeve 28 threadably engages the projecting end ofthe anchored studs and an externally threaded lower end 30 (best seen inFIG. 3) of the break-away members to thereby mount the lamp pole on thefoundation block.

Referring to FIG. 3, in the presently preferred embodiment of thisinvention, each break-away member 26 includes an intermediate portion 32which is recessed or grooved to reduce its cross sectional area. Anupper end 34 of the member is externally threaded, preferably with athread of the same size as that of lower end 30.

Refering to FIGS. 1 through 3, the lamp pole is mounted on thefoundation block by first securely threading a sleeve 28 onto theprojecting end of each anchor bolt 20. To provide for stability of thelamp post, at least three but preferably four, as shown in FIG. 2,anchor bolts are equally spaced from each other to coincide with thespacing of mounting holes 24 in mounting fiange 22. Next, a break-awaymember 26 is threadably engaged with each sleeve so that theintermediate portions 32 of the members are disposed upwardly of thesleeves. Nuts 36 are threaded over the upper end of the break-awaymembers so that the lower end of the nuts is adjacent the portions ofthe members having the reduced cross sectional area. Upper faces 37 ofthe nuts are levelled with respect to each other until they lie in acommon horizontal plane and washers 40 are slipped over the upper endsof the break-away members. The mounting holes in flange 22 of the lamppoles are aligned with the'breakaway members and the lamp poles and themounting flange are lowered until a lower face 42 of the flange issupported by washers 40. The mounting flange is now secured to thebreak-away members with upper nuts 44.

After the lamp pole has so been installed on a foundation block adjacenta vehicular traffic bearing surface such as a roadway, it is subjectedto wind loads acting on pole 14, arm 16 and lamp 18, as well as to loadsfrom ice (not shown) that might cling to the lamp post. These forces aretransmitted through the mounting flange to the break-away members.Simultaneously, the break-away members are subjected to forces from theweight of the pole, the arm and the lamp. Depending upon the directionand magnitude of the wind load, as well as on the magnitude of any iceload to which the pole might be subjected, the forces to which thebreak-away members are subjected vary from member to member and mightsubject some of the members to compression while others are in tension.The reduced cross sectional areas in the intermediate portions 32 of thebreak-away members are dimensioned so that stresses in the reduced crosssec tional areas do not exceed the yield strength of the material ofwhich the members are constructed when the members are subjected tomaximum forces. It has become accepted practice in the industry todesign such lamp poles for maximum wind of up to 100 miles per hourwhile the maximum permissible ice load is of course dependent on thegeographic area at which the pole is installed.

The reduced cross sectional area of the elongated members serves as anintentional weakening point at which the mounting of lamp pole shallfail when subjected to dynamic loading from the impact of a movingvehicle when it strikes the pole. If the pole were rigidly mounted,severe damage to the vehicle and injuries to its occupants may result.If on the other hand, the pole gives, that is, .breaks' away under theimpact, deceleration forces acting on the vehicle are reduced to amagnitude at which serious personal injuries or property damages areavoided.

Under dynamic loading, i.e. impact, maximum stresses in the member arecyclical and increase in magnitude with. decreased ductility orincreased brittleness of the material. Thus, for a given cross sectionalarea, materials of high brittleness, such as hardened steel, forexample, can withstand a lesser dynamic load, or have a lesser impactstrength, than materials having a low brittleness, such as an annealedsteel. At the same time, the hardening of materials, particularly steel,increases their tensile and compressive strengths and enables them towithstand static, that is non-dynamic loads of a much greater magnitudethan relatively soft steels.

The combination of these two effects is highly desirable in break-awaymembers 26. Their reduced cross sectional areas at portions 32 permitsthem to withstand the static loading from the weight of lamp pole 10, aswell as from wind and ice loads when they are constructed of aheattreatable material such as steel and have been heat treated toincrease their strength. The greater hardness of the members, however,reduces their impact strength and enables them to withstand lesserimpact loads than if they had not been heat treated. Thus, the reducedcross sectionalareas of the members can be dimensioned so that theywithstand the static loads to which they are subjected while failingunder the impact of a vehicle striking lamp post 10.

To maintain the strength of the break-away members at their reducedcross sectional areas it is desirable to protect them at least atportions 32 against corrosion which might, in time, sufiiciently weakenthe member so that it fails under normally expected wind or ice loads.Consequently, if the members are constructed of carbon steel they arehot-dipped galvanized or plated with a suitable metal. Both plating andgalvanizing have adverse effects on the physical properties of steel.The former causes uncertain changes in the shearability of the breakawaymembers at their reduced cross sectional areas. The latter anneales themsince it must be applied hot, thereby nullifying at least a part of thepreceding heat treatment of the member. .-It is, therefore, presentlypreferred to construct the break-away members of a corrosion-resistantmaterial such as stainless steel. Stainless steel does not corrode undercommonly encountered atmospheric conditions, yet it can be heat treatedto give the members the desired hardness. An alternative to usingstainless steel without incurring the above referred to undesirable sideeffects is to coat the break-away members after they have been installedwith rust preventative compound such as tar, paint, greases, etc. Thesecompounds have no adverse effect on the physical property of thematerial of which the break-away member is constructed.

After the lamp pole has been mounted as described above, suitableenclosures, indicated in phantom lines in FIG. 1, may be provided toenhance the appearance of the base of the lamp post or to preventunauthorized persons from tampering with electrical wiring 46 or themounting of the pole. Such enclosures, however, are not necessary forthe practice of this invention.

Although it is presently preferred to construct breakaway member 26 withan undercut so that its threaded ends 30 and 34 have like diameter andthreads as the projecting end of anchoring studs 20 to economize in theproduction of sleeve 28, the break-away member can, of course, beconstructed without such an undercut. In that case the break-awaymembers are. dimensioned so that they have cross sectional area overtheir full lengths which are equal to that of portion 32 of thebreak-away member 26 shown in FIG. 3. Since the members are constructedof relatively expensive materials, i.e. heat treatable stainless steel,the weight savings result in substantially lower manufacturing costs forthe break-away members.

Another distinct advantage of the present invention is that it permitsrigidly mounted poles to be converted into break-away poles. Rigidlymounted poles are frequently constructed identical to the constructionof lamp pole and include the mounting flange 22. The flange, however, isdirectly secured to the upwardly projecting threaded end of anchor studs20. To convert the pole into a breakaway pole, the nuts (not shown)securing the flange and the pole to the anchoring studs are removed andthe lamp pole is elevated a sufficient distance above foundation block12 to permit the installation of the break-away members 26 with sleeves28. After the break-away members are installed and lower nuts 36 havebeen levelled with respect to each other, the lamp pole is lowered sothat upper end 34 of the break-away members are disposed in the mountingholes of the flange. The lamp pole is then secured to the break-awaymembers as described above. The raising of the pole to install thebreak-away base support therefor as above described may normally be donewithout requiring the disconnection of electric lines and the like whichmay be connected to the top of the pole.

It will now be apparent that the break-away base support of the presentinvention may be easily and readily applied at relatively low cost to awide variety of poles and standards used along side of roadways forlighting, signaling, utilities and for warning and directional signs;and that such improved base support may be reinstalled with equalfacility and low cost after being severed in the performance of itsimpact attenuation function.

We claim:

1. A breakaway base support for roadside poles subject to being struckby wayward automotive vehicles, said pole having a horizontal basemounting flange and a plurality of horizontally spaced vertical openingstherethrough, a foundation, a plurality of elongated vertically setbolts mounted in said foundation and having externally threaded upperends projecting vertically therefrom in substantially parallel relation,a plurality of elongated sleeve members having internally threaded endsone each threadably mounted on one of said bolt ends and havinginternally threaded upper end portions extending vertically from saidbolts, aplurality of elongated breakaway members having first externallythreaded ends one each threadably mounted in an upper end portion of asleeve and having second externally threaded ends extending verticallytherefrom and being mounted through said flange openings, means on saidsecond ends of said breakaway members and providing a level platformsupport for the underside of said flange, nuts threadably mounted onsaid second ends of said breakaway members and bearing on the upper sideof said flange for clamping said flange between said means and nuts,said ends of said breakaway members and said bolts having asubstantially equal cross-sectional area and a mid-portion of saidbreakaway members between said sleeves and means having a relativelyreduced cross-sectional area, said breakaway member being composed of amaterial having lower ductility and higher ultimate strength than thematerial of said bolts and said mid-portion being dimensioned to providecompression and tensile strengths substantially equal to the compressionand tensile strengths of said bolts and impact shear strengthsubstantially less than said bolts.

2. A breakaway base support as defined in claim 1 wherein said breakawaymembers are formed of heat treatable stainless steel.

3. A breakaway base support as defined in claim 1, said means comprisingnuts threadably attached to said second ends and providing adjustableleveling of said platform support.

References Cited UNITED STATES PATENTS 2,638,368 5/1953 Weinberg 285-21,334,519 3/1920 Bushong 52295 1,481,187 1/1924 Clay 52295 2,128,294 8/1938 Gage 52295 3,289,369 12/ 1966 Marcus 52295 3,355,998 12/1967Roemisch 94-1.5 1,027,782 5/ 1912 Watrous 1 EDWARD C. ALLEN, PrimaryExaminer Us. o1. 12, s s 1; 248-458

